U.S. Pat. No. 3,374,938 to Pierce, Jr., assigned to the present assignee, is directed to an article carrier of the wraparound type in which the bottom panels are secured in overlapping relation. A plurality of tongues on one of the bottom panels is threaded into corresponding transversely elongated apertures in the other of the bottom panels. Each of the tongues has a locking tab longitudinally aligned therewith for disposition in the same transversely elongated aperture as the tongue. When the carrier is erected and filled, the tab is punched through the aperture by the packaging machine to lock the panels together. Each of the tongues is threaded in the position to have an edge to edge engagement with a transverse locating edge of the corresponding aperture. Each locking tab, after being punched into position, also has an edge to edge engagement with the opposite transverse edge of the aperture to lock the overlapping bottom panels of the elongated blank to form the carrier.
During the retail life of these carriers, many are subject to rough handling and other conditions having a tendency to loosen or release the locks. Also, the carriers are routinely exposed to refrigerated conditions. Under such conditions the paper with which the carrier is formed may absorb moisture and consequently lose stiffness. This causes the locks to be more susceptible to inadvertent lock release. Because of this, improved locking strength and lock protection is a vital concern continually sought by those skilled in the packaging art. As will be seen below, the carrier of the present invention is an improvement over the prior art Pierce carrier in that it does establish and retain better edge to edge relation along two substantially parallel, transversely elongated slits, and provides lock protection by providing a protector strap which overlies the tab along the interior of the carrier.
U.S. Pat. No. 4,200,220 to Ganz is also part of the prior art. This patent is also directed to an article carrier of the wraparound type in which the bottom panels are secured in overlapping relation. The tongues on one of the bottom panels are threaded into corresponding transversely elongated slits in the other of the bottom panels, but this is done only after doubling over each bottom panel wth a fold of 180.degree.. Each of the tongues has a tab longitudinally aligned therewith for disposition in a cooperating elongated slit on the opposite bottom panel. However, when locked in place, there is no edge to edge engagement for the best locking performance. Instead, the tab lies in a plane substantially perpendicular to the plane in which the tongue lies.
This carton requires complicated machinery to perform the doubling over folds and threading of the tongue and tab. Also, the tab which extends vertically into the interior of the carton is susceptible to damage by the articles within the carrier and in a damaged state, likely to slip back through the receiving slit. The doubling feature greatly increases the cost of the carrier due to the increase in paperboard required.
Thus, the need for an improved article carrier lock that is more secure and reliable is identified. In this regard, it is contemplated that the lock should have a tab and tongue extending in opposite directions within substantially the same plane, thereby providing a secure edge to edge engagement, and including a protective arrangement for improved lock retention and for additional strength and support.